It is known to use acoustic fluid sensors particularly ultrasonic fluid sensors in the oil and gas industry for measuring multi-phase fluid flows. Since such fluid flows may occur at raised pressures, steel pipework has historically been used to provide the structural strength required to provide pressure integrity for such fluid flows.
Acoustic fluid sensors are known in which acoustic transducers are located externally of a steel pipe. The transmission of acoustic energy through the steel pipe into a fluid flow path defined by the steel pipe may be low and such acoustic fluid sensors may not be capable of providing measurements of sufficient accuracy and/or sensitivity for some applications.
Other known acoustic fluid sensors include a steel pipe having one or more apertures formed through the wall thereof. Each aperture is fitted with a window such as a quartz window for the transmission of acoustic waves into and out of a fluid present within the pipe. However, such a window may weaken the pipe and may be difficult to seal for pressure integrity. Moreover, where such a window is located within a recess defined within a wall of the steel pipe, the window may be susceptible to the accumulation of deposits or contamination which may have a detrimental effect on the transmission of acoustic waves through the window and which may degrade sensor performance.